The present invention relates to a laser spot locating device and to a laser spot locating system including same. More particularly, the present invention relates to a scan-free, daylight operative, laser spot locating device and further to a system including same along with a laser designator.
Accurate location of a low frequency pulsed laser spot in a large field of view is typically effected by a four quadrant detectors device which further includes gimbals and a servo loop used to scan the four quadrant detectors of the device until the laser spot is located in the center of the field of view of the device.
This gimbals and servo loop based device demands a long chain of laser pulses for location, due to the gimbals and servo loop, it is very expensive to manufacture, it is cumbersome, and above all, it is relatively slow in locating laser spots, e.g., about 10 seconds per location.
In order to simplify the device by elimination of the gimbals and servo loop, defocusing of the spot to about a quarter of the field of view is employed. The position of the spot is thereafter determined by the ratio of the defocused spot on each quadrant detector, thereby obviating the need for the gimbals and the servo loop. However, due to defocusing, the accuracy of such a device is very low.
Charge transfer devices (CCDs, CIDs or active pixel devices), which also obviate the need for gimbals and servo loop due to their inherent array of radiation-sensitive elements, are usable for laser spot location only when employed in combination with strong CW lasers that consume a large amount of power, or with less powerful lasers when there is a very low background radiation, (as at night time or inside a machine). In daylight, however, such devices results in a very poor sensitivity (i.e., low signal-to-noise ratio), rendering such devices inoperative.
There is thus a widely recognized need for, and it would be highly advantageous to have, a daylight operable, scan-free laser spot locating device and system devoid of the above limitations.